1. Field of Use
This application relates to and is co-pending with U.S. patent application Ser. No. 732,891, filed May 8, 1985, by Larry J. Oliphant and entitled "MEANS TO REDUCE OSCILLATORY DEFLECTION OF VEHICLE" and which was allowed on Sept. 4, 1985. This application also relates to and is co-pending with U.S. patent application Ser. No. filed 798,333, filed Nov. 15, 1985, by Larry J. Oliphant and entitled "CONTROL FOR DEFLECTION REDUCTION MEANS", which is a divisional of Ser. No. 732,891 now U.S. Pat. No. 4,573,592. The two aforementioned applications and the instant application are by the same inventor and are assigned to the same assignee.
This invention relates generally to vehicles, such as mobile cranes or the like, which have a load-handling boom pivotably mounted on the vehicle chassis. In particular, it relates to a deflection reduction system for reducing or preventing bouncing or porpoising of the chassis as the vehicle moves across terrain. More specifically, it relates to such a system which employs a deflection reduction module which is mechanically mountable on a boom hoist cylinder on the vehicle and to valve means for hydraulically connecting the module to the boom hoist cylinder.
2. Description of the Prior Art
As explained in the aforesaid U.S. patent applications and hereinafter, in vehicles of the aforesaid type the chassis is supported on resiliently compressible balloon tires and may also employ axle springs. When the vehicle is to be moved between job sites, the boom, which is pivotably mounted on the chassis and can be raised and lowered by a boom hoist cylinder, is lowered and rigidly secured to the chassis in road-transport position. As the vehicle moves across rough terrain or accelerates or decelerates rapidly, the heavy mass of the vehicle tends to generate dynamic loads on the vehicle axles which cause the chassis to oscillate or deflect angularly and vertically (i.e., bounce or "porpoise") relative to the terrain over which it travels. This is a dangerous condition. The aforementioned allowed U.S. patent application Ser. No. 732,891 discloses deflection reduction means for reducing or eliminating such chassis deflection. Such deflection reduction means presupposes that the boom is unrestrained and free to pivot (i.e., deflect) relative to the chassis and comprises components which are embodied in a double-acting boom hoist cylinder, namely, a resiliently compressible and expandable spring effectively connected between the boom and chassis and clamping means (also effectively connected between the boom and chassis and in the form of a volume of compressed gas to reduce the speed of spring motion as rapidly as possible to thereby dissipate the dynamic loads. Such deflection reduction means also comprises suitable valve means to bring the said components into play when needed. Such deflection reduction means, being embodied in the boom hoist cylinder, require a boom hoist cylinder of special construction.